Industrial metals, especially the industrial ferrous metals, are used in a great variety of applications in natural environments, such as pipes, bridges, ships, towers, oil and gas drilling rigs, marine piping and valves, rock mining equipment, electrical facilities, and pipe lines for the transport of fluids and slurries. Corrosion protection for ferrous metals used in various natural and artificial environments is provided by coatings such as paints, wrappings and galvanizings, and metal laminations. There are many patents and literature articles directed to the prevention of corrosion of ferrous metals. There are many ferrous alloy formulations known as stainless steels that are corrosion resistant. However, stainless steel is expensive and coatings of paint, plastics, hydrocarbons and galvanizings are not permanent, especially in corrosive geochemical environments such as marine environments and various underground environments within soil and rock. It is common knowledge that the ferrous metal members of bridges, for example, have to be protected from corrosion, usually by galvanizing or painting. Components of ships require constant attention by painting to retard corrosion of the metal by sea-water.
It is generally understood and accepted that ferrous metals and alloys thereof will become corroded and decomposed by rusting within several to tens of years when exposed to the weather, or used in marine and underground applications, or used in corrosive enviroments such as boilers and heat exchangers. Many various coatings used to retard corrosion of ferrous metals are themselves unstable in natural environments.
Awaruite is the mineral name for naturally occurring iron-nickel alloys having the .gamma.' (gamma-prime) structure. The most common composition of awaruite corresponds to the formula FeNi.sub.3 which is that of an ordered, stoichiometric phase. Awaruite may contain small amounts of copper and cobalt metal, e.g., less than about 5 atomic percent each. It is formed in nature during the hydrothermal alteration of ultramafic rock (serpentinization) at temperatures around 300.degree.-400.degree. centigrade. Awaruite is known both as a mineral component of altered ultramafic rocks and as detrital grains in sediments produced by the erosion of altered ultramafic rocks. In both examples it has been shown that the awaruite has survived for thousands to millions of years. Awaruite is stable over wide ranges of Eh, pH, temperature, pressure and varying compositions of groundwater. Awaruite is stable in groundwater containing substantial amounts of chloride ions, oxygen and other solutes in natural geochemical environments.
The ranges of compositions and temperatures within which alloys of iron and nickel have the ordered face-centered cubic structure (.gamma.' or gamma-prime) have been studied by Josso.sup.(1) (1950), Geisler.sup.(2) (1953), Viting.sup.(3) (1957) and Heumann and Karsten.sup.(4) (1963). The single-phase stability field for .gamma.' is centered about the composition FeNi.sub.3 ; see FIG. 1. The stability field first appears at approximately 500.degree. C. and broadens to compositions with greater and less nickel with decreasing temperature. The single-phase stability field of .gamma.' is separated from the single phase field of disordered face-centered cubic iron-nickel alloys (.gamma. or gamma) by a two-phase region of co-existing .gamma. and .gamma.'. At temperatures below 345.degree. C., relatively nickel-poor .gamma.' alloy transforms to a two-phase assemblage of .alpha. (alpha) iron and .gamma.' alloy. This transformation may be inhibited or prevented at low temperatures by slow kinetics. FNT (1) See footnote (1) at end of specification. FNT (2) See footnote (2) at end of specification. FNT (3) See footnote (3) at end of specification. FNT (4) See footnote (4) at end of specification. stability field boundaries are disputed. Low-temperature data of Heumann and Karsten indicate that the .gamma.' field is broad. This result is supported by the high-temperature differential-dilatometry data of Josso as it is interpreted by Geisler. The interpretation of the phase boundaries by Viting, based on electric resistance, microstructure and differential thermal analyses data, shows a much narrower single-phase stability field for .gamma.'; see FIGS. 1 and 2. At 400.degree. C., the single-phase .gamma.' field extends from about 64 to about 83 atomic percent nickel according to the diagram of Heumann and Karsten, whereas the single-phase .gamma.' field extends from about 72.5 to about 78 atomic percent nickel according to the results of Viting.
Reported compositions of terrestrial iron-nickel alloys range from 64 to 96 atomic percent nickel, but occurrences of natural, single-phase alloys known to have the .gamma.' structure exhibit a more limited range of compositions, supporting the interpretation of Viting of a narrow .gamma.' field; see FIG. 3.
The preparation of a wide variety of nickel-iron alloys is known to the art. For instance, U.S. Pat. No. 1,762,730 to McKeehan discloses alloys of nickel and iron which contain 60% to 80% Ni. The alloys are stated to have desirable magnetic characteristics. U.S. Pat. Nos. 4,192,765 and 4,337,167 in the name of John M. Bird et al disclose the use of nickel-iron alloy as a container for radioactive nuclear waste.